Process for testing frangible vessels



Navo 30 1926.

1,608,514 A. J. LOEPSINGER PROCESS FOR TESTING FRANGIBLE VESSELS Filed Jan. 1925 14159)"! Jloe asz nyw' INVENTOR.

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Patented Nov. 30, 1926.

UNITED- STATES PATENT OFFICE.

ALBERT J. LOEPSINGER, OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO GENERAL FIRE EXTINGUISHER CQMPANY, OF PROVIDENCE, RHODE ISLAND, A CORPORA- TION OF DELAWARE.

PROCESS FOR TESTING FRANGIIBLE VESSELS.

Application filed January 21, 1925. Serial No. 3,778.

This invention relates to improvements in process for testing frangible vessels.

More particularly it relates to automatically frangible vessels of the general type shown in my Letters Patent No. 1,290,602 of January 7, 1919, in which the vessel is illustrated as it may be used as a frangible strut in an automatic sprinkler for a fire extinguishing system. When used in this connection the bursting of the vessel, by rise of temperature, sets off the sprinkler. The vessel is a small bulb made of some material such as glass, or preferably fused silica, which is sealed containing a liquid which when heated expands faster than the glass or silica walls, and also containing a small bubble of air or other gas which is but sparingly soluble in the particular liquid contained. Rise of temperature first drives the air into solution in the liquid by the differential expansion, which finally fills and causes fracture of the vessel, and the latter bursts with a shattering action, owing to the sudden liberation of the air from the liquid.

For the perfect and reliable operation of such apparatus in practice, it is important to be able to ascertain in advance whether any particular specimen is in condition to operate whenever the predetermined temperature shall be applied to it. It is a part-1cular object of the present invention to provide a device for ascertaining whether there are any minute cracks in the container walls, the presence of which might adversely affect the operativeness of the bulb and thus fail to set off the sprinkler in which the bulb is set. This device, as herein described, comprises a novel process or interaction of elements to which the air and li uid thereof are to besubjected, and invo ves the making of the frangible vessel with such walls, liquid and gas as will respond to the process.

In the process of manufacture of such bulbs, as disclosed in my said patent, the

frangible vessel is complete when it has been converted into a sealed enclosure containing aliquid which fills it completely at ordinary temperature except for the presence of a small bubble of gas which is sparingly soluble in the liquid, and which most conveniently may be air. With rise of temperature the liquid expands more rapidly than do its containing Walls, and the heavy pressure thus put upon the bubble of air gradually forces the air into the liquid. However, if there were a minute crack this air might be forced out through the wall instead of being forced into the liquid, and the walls would not then burst with the desired shattering effect. In the operation of such apparatus the liquid does not burst the walls until it reaches a temperature a few degrees above that at which it actually fills the entire interior of the receptacle. Hence the bubble can be made to disappear by heating the bulb, without fracture of the vessel, and can then be made to reappear by cooling the bulb. It is a feature of the invention to select, for the frangible Vessel, substances in which there is a certain reluctance of the gas to reappear upon such cooling, due apparently to some form of retention by the liquid. In such a case, the vessel can be tested for tightness of the containing walls by the method of the invention; the whole having been heated to a temperature at which the bubble has disappeared, because of the expansion of the liquid to fill the whole interior of the Vessel, and the whole being then cooled, if the walls are tight the bubble does not immediately reappear, owing to the said reluctance. However, the contraction of the liquid, or its tendency to contract, exerts a force which tends to create a vacuum and which will suck strongly through any small crack that may exist in the wall of the vessel. It follows that if there be such a crack the bubble of air will reappear gradually, consisting of air drawn in through such a crack; and the vessel may be discarded as being imperfect. But if there be no such crack there will be a delay during the initial cooling, during wvhich the tendency of the liquid to contract becomes stronger and causes an increasing tension, which finally becomes great enough to overcome the resistance of the liquid, by which the gas is being held in the solution,and the bubble will then reappear. WVhen this occurs the bubble appears suddenly and with a slight sound, as the gas leaps into bubble formation. Such a result indicates that the wall of the vessel is tight.

It is therefore a part of the invention to select for the materials a liquid and a gas which will produce this action, instead of of the tube may be formed into a bulb by melting and closing it with a tight wall at one end, and by drawing its other end into a snout, left open. This bulb may then be placed in a bell jar; and the air being evacuated from the jar to a high degree, the bulb may be filled with the said liquid by running the same into the jar. A number of bulbs may be thus treated together in the same vacuum space. aving been thus filled, they may be taken out and immersed in a water bath whose temperature may be raised to a value somewhat below that at which they are intended to burst. If, for

, example, they are intended toburst in the near vicinity of 135 F, they may be thus heated to a temperature ofabout 119 which will cause some of the liquid in each to; be ejected. through the upstanding snout. vThen each bulb may be placed inv a. smallqvessel where it is surrounded by water.. The wateribeing then frozen, the liquid in the bulb becomesv cooled to the freezing pointof water and contracts correspondingly, so

that a. small quantity of air enters the snout and. bulb. Then the bulb may be sealed, by closing its snout by fusion. During this step in the process the ice blanket keeps the body of liquid in the bulb cool, so that the liquid does not expand and fill the interior; and'when the sealing has been completed the bulb, will 7 be found nearly filled with liquid and having its remaining space filled with airin the form of a bubble.

The severity of stresses withinthe walls of the container is greatly minimized when the bulb ismade of the material above described,

a bulb is thus defective.

but even then there is danger of some of the bulbs proving defective in tightness. Thev process ofthe invention indicates whether By raising the bulb and contentsnearly to the temperature at which bursting is expected, that is, close enough thereto for the bubble therein to have disappeared from view, a condition is created in which the air has been driven into the liquid, it being understood that the liquid is one which wets the wall, ofthe container. This, disappearance occurs gradual lywith rise of temperature. After the bulb tures, eXce.

1,eos,514

has rested in this said condition for any desired length of time, the temperature may then be reduced gradually; and if the bubble gradually reappears it will be known that the wall of the receptacle is not tight. But if the reappearance of the bubble is delayed until the temperature has had a considerable fall, andv then occurs suddenly and with a snapping sound, it will be known that the walls of the vessel have withstood the suction caused by the tendency of the liquid to contract at a faster rate than the walls, until that suction became great enough to overcome the surface tension or whatever may be the cause which tends to keep the gas in solution under the circumstances stated. The reliability of this test having been found in practice, it is not necessary to know the exact nature of the physical changes which occur, as between the air and the liquid. It

is convenient and sufficient for the purposes of the present specification, to speak of this as a going of the air into solution in the liquid, and as an inability of the air tobreak out from the liquid, upon initial cooling, owing to the confining surface tension of the liquid, because these termsdelme what appears to occur; But if it should be found that the above described phenomenon is more probably an adsorption of the liquid on thewalls of the container sorthat it'is the adsorption or the tensile strength of theliquid which has to be overcome, or is some other variety of adsorption possibly of the air on the surface of the liquid orwithin the liquid, it will nevertheless be understood that such a discovery does not alffect the Practice of the invention as above set forth, nor limit the scope of the patent as defined in the claim, to anything less than that process which actually occurs when the steps herein set forth are taken. c

It is intended that the patent shall cover by suitable expression in the appended claim, whatever features of patentable novelty exist intheinvention disclosed. V i

The accompanying drawing illustrates an embodiment of the invention and two stages of the practice of. the process:

Figure l is a side elevation of the frangible vessel which is to be tested showing its, normal appearance at ordinary temperapt that the size of' the bubble is somewhat exaggerated; V V

Figure 2 1s a side elevation. of the same showing its appearance during the; test, at.

astage when by rise of temperature the bubble has been driven from view; and

Figure 3 is a similar elevation showing the same vessel just after being cooled to a sufficient extent so that the bubble has suddenly reappeared. with. a snap as above described, thus demonstrating the tightness of the walls. c. 7

Referring to the drawings '10 indicates the fused quartz container, in which is the liquid 11 which entirely fills it except for the space occupied by the bubble 12. This vessel has the initially closed end 1 1 and the snout 16 which has been sealed at its point 18. Upon the application of heat to the vessel shown in Figure 1 the liquid 11 expands, faster than the wall expands, causing the gradual diminution of size of the bubble 12 until it disappears from view as in Figure 2. The whole being then cooled the aspect remains unchanged during the early part of the cooling until the bubble suddenly reappears as at 12, in Figure 3, where its reduction in size is also slightly exaggerated. WVith further cooling the size of the bubble grows until the normal aspect is reached as in Figure 1. If, however, the vessel is defective because of having a crack in its wall the heating may produce the change which is illustrated from Figure 1 to Figure 2; but upon cooling the initial contraction may draw in air through the crack so that the bubble promptly reappears of a size much smaller than is shown in Figure 3 and grows gradually until the size of Figure 1 is reached at a normal temperature; and this course of events indicates that the vessel is not tight.

In order to get a strongly definitive snap action in the reappearance of the bubble and to have the other characteristics which are advisable for the liquid in such a frangible vessel, as set forth in my said patent, I prefer to use tetrachloroethane as the liquid. I have discovered that this substance holds the gas for a relatively long range of temperature reduction, before letting it resume bubble form; and then releases it with a correspondingly violent reaction which is easily discernible by the person conducting the test.

I claim as my invention:

A method of testing the tightness of the wall of a closed vessel containing a liquid, having a coefiicient of expansion exceeding that of the vessel, the quantity of said liquid being sufiicient nearly to fill the vessel, and a bubble of gas which is only sparingly soluble in the liquid and which when in solution remains in that condition, as the liquid cools, to a temperature below that at which the bubble of said gas was made to disappear by rise of temperature; said method consisting in heating the whole until the expansion of the liquid and its solution of the gas has caused the liquid to fill the vessel so that the bubble has disappeared; then cooling the whole, whereby there is contractile stress of the liquid tending to a re-forming of the bubble, and observing such reformation of the bubble, which re-forming occurs gradually if there be leakage from without, but is deferred to a lower temperature and forms suddenly upon the overcoming of the tensile strength of the liquid if there be no such leakage.

Signed at Providence, Rhode Island, this fifteenth day of January, 1925.

ALBERT J. LOEPSINGER. 

